An organic light-emitting diode (OLED) can convert pairs of charge carriers injected into an organic emitter layer to photons, each pair being formed from an electron and a hole. In an OLED with only one emitter layer, a maximum of one photon can be generated per pair of charge carriers injected. In order to achieve higher efficiency, it is known to stack multiple emitter layers one on top of another, wherein a charge generation layer (CGL) is arranged between adjacent emitter layers in each case. As a result, it may be possible to generate multiple photons per pair of charge carriers injected into such a stack, since the charge generation layers act as internal anodes and cathodes.
A CGL generally has a p-doped region and an n-doped region, which are connected together via an intermediate layer. A disadvantage of such a construction, in which the CGLs represent additional layers to those necessary for light emission, can lie in the fact that the CGL layers employed often absorb in the wavelength range in which the OLED emits, resulting in a decrease in the efficiency of the OLED. Conventional commercially available p- and n-dopants are, moreover, often expensive compared with other materials of an OLED. Furthermore, a conductivity doping can generally bring about a strong temperature-dependence of the operating voltage and it is therefore assumed that this also constitutes one of the limiting factors for the stability of OLEDs at high temperatures.